The present invention relates generally to welding-type devices, and more particularly, to an assembly for igniting or stabilizing an arc of a welding-type device. Specifically, the invention is directed to a spark gap assembly of a welding-type device for arc ignition or stabilization.
In some welding-type processes, it is often desirable to employ a high frequency voltage signal in starting or maintaining an arc. In doing so, a high voltage, high frequency signal is generated and applied across an arc gap, e.g. from a torch to a workpiece. This may be done initially to establish an arc, to maintain an arc in the event of arc rectification, or continuously. Thus, an arc may be ignited or stabilized without actual contact occurring between the torch electrode and the workpiece. The use of a high voltage, high frequency signal is equally applicable for igniting both AC and DC welding arcs. In AC arc systems, arc rectification is prone to occur when the welding voltage signal from a welding-type power source cycles through a null point. In such a case, a high voltage, high frequency signal could be applied at each null point in the frequency cycle of the welding voltage signal, or as necessary to correct rectification.
One method of producing a high voltage, high frequency signal for such an application is through use of a spark gap assembly. A high voltage signal is applied to spark-inducing elements such that a spark is periodically generated across a small gap between surfaces of spark-inducing elements. A typical spark gap assembly includes a number of spark gap points held in place by various securing means. As used herein, “spark gap point” will refer to the conductive elements across which a high voltage signal is applied. Known spark gap points have a spark gap surface at only one end of the body of the spark gap point. “Spark gap surface” refers to those conductive surfaces between which a spark arcs.
Spark gap points are typically arranged such that the spark gap surface of one point faces the spark gap surface of another point. The spark gap surfaces are separated by a distance known as a spark gap. Such systems usually include one or two pairs of spark gap points, although use of more than two pairs is possible. When one pair of spark gap points is used, a single spark gap is defined between the spark gap surfaces of the points. Likewise, if two pairs of spark gap points are used, two spark gaps are defined. That is, one spark gap is created between each pair of points, and a jumper wire is used to electrically connect the two pairs. Conventional spark gap assemblies utilize pairs of spark gap points and, as such, two spark gap points are necessary to form one spark gap. Therefore, known spark gap assemblies may contain an unnecessary number of parts, and as a result, may be unnecessarily complex and costly to manufacture and assemble.
Conventional spark gap assemblies having two spark gaps, i.e. two pairs of spark gap points, are constructed so that the required four spark gap points are aligned along two separate rows. Because the spark gap points must be arranged in this manner, the size of a spark gap assembly is increased and a jumper wire is necessary to electrically connect the pairs of spark gap points. Additionally, requiring two separate rows of spark gap points in the same assembly limits the possible shapes of the assembly. And, the use of an extra wire creates an additional possibility for electrical shorts or circuit breakdown, and could vary the electrical resistance between spark gaps.
Such an assembly also presents increased construction complexity and manufacturing costs. Constructing a spark gap assembly is made more difficult when there are multiple rows of spark gap points. This is due to the precise alignment desired for spark gap points arranged along multiple axes. Precise alignment of spark gap point housings, threaded screw holes, and other securing means must be performed twice, once for each separate row of spark gap points. Furthermore, the use of more parts increases production costs. For example, jumper wires present not only added part costs, but also added construction steps since they must be soldered or otherwise electrically connected to the spark gap points.
Conventional spark gap assemblies are also prone to misalignment when in use. Under certain operating conditions, it may be expected that some components will become unfastened. This is especially significant in spark gap assemblies, where precise alignment is critical. Therefore, as more parts are used, the possibility of spark gap surface misalignment increases. In addition, the type of fastening or securing means used can affect an assembly's propensity for misalignment. Known spark gap assemblies use methods of securing spark gap points which may not be optimal. For example, when fasteners do not directly engage a spark gap point, the spark gap point may be more likely to shift within its housing.
Also, the method of applying a high voltage input signal to spark gap points can affect performance. Typical spark gap assemblies employ a method of indirectly conducting input voltage signals to spark gap points. Frequently, the high voltage input is applied to a heat sink or securing means to be conducted to the spark gap points indirectly. Performance of a spark gap assembly can be increased by applying the input voltage signal directly to the spark gap points, rather than indirectly conducting the signal through other components.
It would therefore be desirable to have spark gap points and a spark gap assembly for welding-type devices which provide spark gaps using fewer parts. In particular, it would be desirable to have a spark gap assembly constructed such that the spark gap points may be inline, rather than arranged in multiple rows. Such an arrangement would require fewer parts, reduce the expense and complexity of manufacturing, and would be less prone to misalignment. Additionally, providing for application of a high voltage signal directly to spark gap points would improve performance.